The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An antenna module may be used for integrating various functions of vehicle roof antennas. There are known microstrip patch-antennas, which include a substrate having a lower surface with metallization of the entire area thereof and an upper surface with a suitable metallic structure or antenna structure thereon. Such microstrip-patch-antennas commonly have a very narrow frequency bandwidth, for example, one percent to two percent relative bandwidth, unless additional measures are taken. By employing parasitic elements, bandwidth may be increased or multiple frequency bands may be blocked. These parasitic elements are conduction or surface structures, which are present on the same or higher plane than that of the antenna structure. If the parasitic elements are on a higher antenna structure, then they are coupled to the lower antenna structure, wherein a common HF-connection cable on the lower antenna structure runs to an amplification unit. In the parasitic elements, high frequency currents are induced, which adapt to the shape and dimensions of the parasitic elements and thereby produce fields. As a result, the entire structure has the capacity to send and receive both neighboring as well as somewhat distantly spaced frequencies.
But antenna structures of the above-described type are only suitable if the entirely expanded frequency band is allocated for the same service. When multiple, independent services are intended, then antenna modules with separately built antenna elements arranged next to one another are then used. In this configuration, however, more space is required. Furthermore, sufficient isolation is required for the proper function of the individual antennas elements.